One of the most important present-day endeavors when designing drive units for various purposes relates to minimization of fuel consumption so as to achieve the most effective and environmentally-friendly operation of the drive unit. Depending on the respective purpose, weight reduction might also be paramount, for example in the case of drive units in vehicles. At present, for the purpose of optimization of fuel consumption in aircraft, the use of fuel cell systems is known in order to provide electrical power and in this way to partly reduce the mechanical power to be provided by main engines, some of which mechanical power is used to drive electrical generators. In order to simplify the provision of fuel for simultaneous operation of engines on the one hand, and fuel cells on the other hand, catalytic reformers are frequently used that from a hydrocarbon-based fuel provide a suitable fuel cell fuel so that in the vehicle concerned only a single type of fuel needs to be provided.
Parallel operation of engines and fuel cells that primarily provide mechanical power, in which engines and fuel cells there is either complete separation in spatial and functional terms or coupling takes place only by way of operating media in the form of fuel and air and/or from a thermal point of view by means of heat exchangers, could be further improved in order to exploit maximum possible efficiency.